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Date: Tue, 2 Feb 1999 08:52:20 +0100 (MET)
Message-Id: <199902020752.IAA08445@beta.informatik.hu-berlin.de>
From: Sven Wischnowsky <wischnow@informatik.hu-berlin.de>
To: zsh-workers@sunsite.auc.dk
In-reply-to: "Bart Schaefer"'s message of Mon, 1 Feb 1999 09:02:46 -0800
Subject: Re:  Associative array ordering and selective unset (Re: Example function)
X-Mailing-List: <zsh-workers@sunsite.auc.dk> 5157


Bart Schaefer wrote:

> ...
> 
> We could go the ksh route and make `noglob unset foo[key]` work.  Like:
> 
> 	function unset() {
> 	    emulate -R zsh
> 	    setopt localoptions extendedglob
> 	    local arg i
> 	    for i
> 	    do
> 		arg=( "${(@s:[:)i}" )
> 		if [[ $#arg > 1 &&
> 		    $(eval print '${(t)'${arg[1]}'}') == association ]]
> 		then
> 		    eval "$arg[1]=( \${(kv)$arg[1][(I)^${(j:[:)arg[2,-1]} )"
> 		else
> 		    builtin unset $i
> 		fi
> 	    done
> 	}

Since even `vared' can now understand the subscripted syntax, I think
adding this to unset (even in C) would be a good thing. (I'm pretty
sure people will want to have a easy way to remove key/value-pairs
from associative arrays).

> Can you think of a better idiom than $(eval print '${(t)'${arg[1]}'}') to
> get the type of the variable whose name is the value of $arg[1] ?  I keep
> thinking there ought to be a way with ${(e)...} but couldn't make it work.

When implementing the new completion example stuff I was somewhat
irritated that there is no easy way to get the value of a parameter of 
which one only has the name in another parameter. Trying to get the
type of that parameter is indeed even more complicated.

Hm, `(e)' is used at the very end and I wouldn't like to change
that. Maybe yet another flag? E.g.: `P' makes the thing after the
flags be used as the name of a parameter. So `${(P)foo}' is the same
as `$foo', but `${(P)${foo}}' will take the value of `foo' as the name 
of a parameter and work on it. So your example would become:

  if [[ $#arg > 1 && ${(Pt)${argv[1]}} == association ]] ...

Looking at the code this doesn't seem too hard to implement (well, I
said `seem'...).

Bye
 Sven


--
Sven Wischnowsky                         wischnow@informatik.hu-berlin.de